Hi Guys,

First post on the forum, thanks to the search button.....but I cannot quite figure this one out. Check engine light started coming on a few days ago, intermittent, now it's stuck on. I did the diagnostic and got a code 21, main O2S oxygen sensor. Pulled the EFI fuse and disconnected the negative battery terminal to reset ECU but the CEL is here to stay. Need to get sensor fixed, and if possible, without taking it to a repair shop. A couple of questions though: I am no mechanic, but with proper instruction can tackle the DIY jobs without a problem. Where is the main (front) oxygen sensor, and is this a project I should do myself? The other question: My GS came from original owners in California, and I see that there is a different O2S for California cars, how do I tell if I need the sensor for a 'Cali Car"?

Any replies, thanks in advance. And to the many contributors in this forum, thanks for your help in the past as well...Mike

 

Bump.....anybody?

 

Code 21 is for heater circuit of bank #1 O2 sensor. This is the sensor before the catalytic converter and is the sensor closest to radiator.
You should have no problem replacing sensor.
California spec only monitors sensor different but sensor is same as federal spec. You could actually check resistance in pin #1 and #2. Any value for this code would be acceptable but you will probably find an open circuit which is the reason for light constant on now.